Precision fluid dispenser

ABSTRACT

An apparatus is described for repeatably dispensing precise quantities or amounts of liquid. An actuator operates a reciprocable syringe plunger for drawing liquid into the syringe and discharging same. A valve controls the inflow and outflow of the syringe and spaced permanent magnets hold the movable member of the valve in a position for connecting the syringe either with a source of liquid or in a position for connecting the syringe with a conduit for conveying discharged liquid, until the syringe plunger has been moved by the actuator to the respective ends of its stroke.

United States Patent lnventors John D. Reid Monrovia; William M.Sheppard. Whittier. both of, Calif. Appl. No 814,072 Filed Apr. 7, 1969Patented Aug. 10, 1971 Assignee Hamilton Company Whittier, Calif.

PRECISION FLUID DISPENSER 10 Claims, 6 Drawing Figs.

US. Cl. 417/400, 91/216 Int. Cl ..F04b 17/00, FOlb 15/00 Field of Search103/227,

[56] References Cited UNITED STATES PATENTS 2.645.208 7/1953 Hardesty91/216 2,791,]80 5/1957 Gotham etal. l03/227XR Primary Examiner- RobertM. Walker Atlorney.|. C. Baisch ABSTRACT: An apparatus is described forrepeatably dispensing precise quantities or amounts of liquid. Anactuator operates a reciprocable syringe plunger for drawing liquid intothe syringe and discharging same. A valve controls the inflow andoutflow of the syringe and spaced permanent magnets hold the movablemember of the valve in a position for connecting the syringe either witha source of liquid or in a position for connecting the syringe with aconduit for conveying discharged liquid, until the syringe plunger hasbeen moved by the actuator to the respective ends ofits stroke.

PATENTED Am; I 01971 SHEET 2 [)F 3 (10%? Q Pemf mil/am M She om;

INVENTORS,

PRECISION FLUID DISPENSER BACKGROUND OF THE INVENTION 1. Field of theInvention This invention relates generally to liquid dispensingapparatus for use in medical and chemical research laboratories andindustrial applications, and relates more particularly to apparatus ofthis character for repeated discharge or dispensing of preciselymeasured quantities ofliquid.

2. Description of the Prior Art There are various prior art devicesaimed at repeated reproducible dispensing of predetermined quantities offluids, including liquids. Various problems are encountered in providingsuitable apparatus of this character that is satisfactory in meeting thevery exacting requirements of scientific research laboratories andindustrial applications.

SUMMARY OF THE INVENTION The present invention comprises a syringe andactuating mechanism for reciprocating the plunger of the syringe. Avalve having a movable valve member controls the flow of fluid to andfrom the syringe, said movable valve member having two positions. Whenin one position liquid is admitted to the syringe and when in the otherposition discharge liquid flows from the syringe.

The actuating mechanism is operated by fluid under pressure and has alongitudinally movable cylinder and a piston operable reciprocabletherein, the piston being attached to a piston rod that extendsoutwardly of the cylinder and has a soft iron armature connected orattached thereto externally of the cylinder. The piston rod also has anoperable connection with the movable valve member for moving it from oneposition to the other and vice versa.

The armature is movable between a pair of spaced permanent magnets.

There are stop means for limiting the longitudinal movement of thecylinder in both directions and when the cylinder is at one limit ofmovement the armature is held by one of the permanent magnets whichholds the piston against movement in the cylinder. Pressurized fluid isthen supplied to one end of the cylinder to cause it to move to theopposite limit of movement. When the cylinder reaches said oppositelimit of movement and is brought to a stop thereat pressurized fluidstill continues to exert pressure within the cylinder and effectssufficient pressure on the piston to pull the armature from thepermanent magnet on which it has been held and move the piston rod andarmature and bring the armature into engagement with the other permanentmagnet. At the same time the piston rod moves the movable valve memberto its other position. Pressurized fluid is then applied to the oppositeend of the cylinder and reverse action occurs. Thus the valve is notoperated from one position to the other until the plunger of the syringehas reached one end or the other of its range of movement.

OBJECTS AND ADVANTAGES OF THE INVENTION It is an object of the inventionto provide a precision liquid dispenser that is extremely accurate inreproducibility of precise quantities of liquid repeatedly discharged.

It is another object of the invention to provide a dispenser of thischaracter that has means for controlling the admission of fluid to asyringe and the discharge of fluid therefrom by valve means that is heldin respective operation positions until the plunger of the syringe hasreached respective ends of its range of movement.

It is still another object of the invention to provide a liquiddispenser of this character having magnetic means for holding themovable valve member of the valve in one or the other of its operativepositions until the plunger of the syringe has reached respective endsof its range of movement.

It is a further object of the invention to provide a liquid dispenser ofthis character that is relatively simple in construction and operation.

A further object is the dispensing of very small volumes of liquids.

The characteristics and advantages of the invention are furthersufficiently referred to in connection with the following detaileddescription of the accompanying drawings which represent one embodiment.After considering this example, skilled persons will understand thatmany variations may be made without departing from the principlesdisclosed and I contemplate the employment of any structures,arrangements or modes of operation that are properly within the scope ofthe appended claims.

Referring to the drawings, which are for illustrative purpose only:

FIG. 1 is a front elevational view of a liquid dispenser embodying theinvention, a portion of the upper end being shown in section to show thearmature or valve operating block of the magnetic mechanism in its upperposition;

FIG. 2 is a side elevational view of the same;

FIG. 3 is a view similar to the upper end portion as shown in FIG. Iwith the armature or valve operating block in its lower position;

FIG. 4 is a sectional view taken on line 4-4 of FIG. 1;

FIG. 5, (a), (b), (c) and (d), diagrammatically shows various stages ofa cycle of operation. In these views the right hand side is to beconsidered as the top of the mechanism while the left hand side is to beconsidered its bottom thereof; and

FIG. 6 is a view similar to FIG. 3 showing an alternative arrangement.

Referring more particularly to FIGS. 1 to 4 of the drawings, there isshown a body, indicated generally at 10, of any suitable material,preferably a nonmagnetic material such as aluminum for example. Body 10has a back part 12 upstanding at right angles from the rear ofa base 14which has a lug 16 upstanding therefrom atone side and integral withsaid base and the back part 12.

At the upper end of the back part 12 is a forwardly projecting block,indicated generally at 18, having horizontal upper and lower parts 20and 22 spaced vertically apart to provide a space, indicated generallyat 24. Space 24 has a part 26 at one side, from the inner end of whichis a portion 28 of reduced width and from which extends a furtherreduced width part 30.

Horizontal upper and lower parts 20 and 22 of the block 18 have alignedvertical holes 34 and 36 in which respective permanent magnets 38 and 40are disposed and secured in place by respective set screws 42. The innerfaces of the magnets 38 and 40 are flush with the top and bottomsurfaces of the space 26, except when additional magnetic force isrequired as in the use of large volume syringes or pumps. FIG. 6illustrates the application of two additional magnets 38a and 40acemented to the armature and aligned to meet magnets 38 and 40 nowrecessed into upper and lower parts 20 and 22. These magnets may be ofany suitable type but those used are alnico magnets.

There are also axially aligned vertical openings 44 and 46 in therespective upper and lower parts 20 and 22 of the block 18. In each ofthe openings 44 and 46 is a bearing or bushing 48 and 50 respectively.

An actuator means, indicated generally at 54, is provided and comprisesa cylinder 56 in which is disposed a piston 58 carried by an actuatorshaft 60 which extends outwardly ofthe upper end of the cylinder througha bushing or seal 62 of an end wall, not shown, thereby preventingactuating pressurized fluid from escaping from the upper end of thecylinder, the opposite end of the cylinder being closed by a wall, alsonot shown, which includes a lug 64 having a fluid passage therein butnot shown, a fitting 66 being provided for said fluid passage to which apressurized fluid conduit 68 is attached to supply pressurized fluid tothe lower end of the cylinder through said fluid passage. Adjacent theupper end of the cylinder is a fitting 70 to which a conduit 72 isattached to supply pressurized fluid to the upper end of the cylinder.Shaft 60 has an enlarged upper end portion 74 slidable in the bearings48 and 50 of the block 18.

A relatively flat cylinder bracket, indicated generally at 78, isattached to the cylinder 56. There is an opening 80 in said bracket inwhich the cylinder 56 is disposed, one side of the opening 80 beingdefined by a strap 82. From the hole 80 there is aslot 83 to theadjacent edge of the bracket thus providing a somewhat resilient tongue84 at the end of the strap 82. Tongue 84 has a hole 86 therethrough inalignment with a tapped bore 88 in that portion of the bracket oppositethe tongue, there being a screw 90 disposed in said hole and screwedinto the tapped bore 88 to tighten the strap 84 on the cylinder andsecure the cylinder in its opening 80.

The bracket 78 also has a vertical tapped bore, not shown, which isprovided with screw threads, not shown, and in which is screwed abushing 92 of suitable friction reducing material such as Teflon, forexample, Teflon being the trademark of the Du Pont Company for theirfluorocarbon resins. The bushing may be externally knurled to facilitatescrewing into the tapped bore in the bracket. Bushing 92 has alongitudinally extending bore therethrough for reception of adjustmentnut 94 on which said bushing is slidable so that the cylinder bracket ismovable upwardly and downwardly and is guided by said nut 94 which hasan enlarged knurled part 95. Nut 94 has a tapped bore extendinglongitudinally there through and said nut is screwed onto an externallythreaded adjustment shaft 96 which has a lower end portion screwed intoa tapped bore, not shown, provided therefor in the lug 16. Rotation ofthe part 95 of the adjustment nut effects upward or downward movement ofthe nut 94 and there is a lock nut 100 on the adjustment shaft'below thepart 95 for securing the adjustment nut in adjusted positions. The part95 of the adjustment nut provides a stop for downward movement of thecylinder bracket and hence for the cylinder 56. Shaft 94 is upstandingfrom lug 16 and its axis is parallel to the axis of the actuator means54.

A three port, two position valve, indicated generally at 110 has a part112 from which an externally threaded part 114 extends. The part 112 isreceived in an opening 113 provided therefor in a housing portion 116 ofa valve mounting plate 118 secured to the front side of the block 18 byscrews 119. Housing portion has a bore 120 extending from the inner endand axially aligned with the opening 113. Within the bore 120 is a valveadapter 122 having a bore therein with an annular inturned flange havingthreads for threaded reception of the threaded part 114 of the valve110. Thus the valve is held in position by the adapter 122. Valve 110may be of any suitable well known character but as shown by way ofexample is of the type disclosed in the application of Clark H.Hamilton, for a VALVE, Ser. No. 403,223, filed Oct. 12, 1964, the valve110 however being of such character as to have two operative positionsas will be described hereinafter.

Within the valve adapter 122 is a valve actuator 126 operably connectedto the movable valve member, not shown, of the valve 110. Valve actuator126 has a flange 128 thereon and at its inner end said valve actuatorhas a flattened part with a notch therein, said flattened part beingreceived in a notch 130 ofa valve shaft 132. There is a gear 136 with anintegral collar 138 secured to the valve shaft 132 by means ofa pin 140.Gear 136 is disposed in the space 30 and on said valve shaft 132 is abushing 142 disposed in a bore 144 extending from the rear of the body10. Bushing 142 is retained in position by an external flange at itsinner end which engages the area of the rear wall of space 30 about thebore 144. The end ofthe collar 138 opposite the gear abuts against theinner end ofsaid bushing or hearing 142.

There is also a bearing 148 similar to bearing 142 disposed on valveshaft 132 at the opposite side of the gear 136, said bearing extendinginto the bore of the valve adapter and having its flange engaging theadjacent end of the valve adapter and being engaged by the adjacent sideof the gear 136. A spring 150 is disposed within the bore of the valveadapter 122 and reacts between the bearing 148 and the flange 128 of thevalve actuator, and urge these parts apart. There is a sufflcientclearance between the valve actuator and the valve shaft so that therewill be no binding and the valve readily actuated with rotativemovements of the gear.

Within the spaces 26 and 28 is a traveling block or armature 156 havinga vertical bore 158 therethrough for reception of the upper end portion74 of the actuator shaft 60, said traveling block being secured to saidshaft portion 74 by means of a set screw 160 disposed in a tapped boreprovided therefor. The bore 158 is disposed in a part of the travelingblock that is of reduced width and disposed in the space portion 28. Thetraveling block or armature is of any suitable magnetic material such aslow carbon steel and is illustrated in FIG; 6 and described on line 25pages 5 and 6.

Means for actuating the gear 138 comprises a rack 162 disposed in anotch provided therefor at the free end of the reduced width part of thetraveling block, said rack being secured in said notch by a screw 164.Rack 162 has teeth 166 operably engaging the teeth of the gear 136 andadapted to rotate said gear with vertical movements of said travelingblock 156 which in turn is actuated upwardly and downwardly withcorresponding movements of the actuator shaft 60. The traveling block156 moves between the magnets 38 and 40.

A syringe, indicated generally at 170, has a transparent barrel 172 anda plunger 173 on a plunger rod 174 having a flange 176 at its outer,free end. The syringe may be of any well known type for handling liquidsor gases and is removably attached to the valve 110 by any well knownmeans. For example, a luer lock is used and includes a female part 178on the valve 110 and a male part 180 on the forward end of the syringebarrel. Thus the forward or upper end of the syringe is securely held inposition.

The plunger rod is secured to the cylinder bracket by placing thepressure member or flange 176 in a recess 178 in the cylinder bracket.There is also a notch 180 to accommodate the adjacent part of theplunger rod so that there is proper alignment of the parts of thesyringe, said flange being held in position by a thumb screw 182disposed in a tapped opening provided therefor in the portion of thecylinder bracket below the recess 178. The syringe may, of course, beinstalled in the mechanism or removed therefrom and various types andsize of syringes may be used. l

A conduit 186 connects the valve 110 with a source offluid to bemeasured and there is a conduit 188 connected to said valve fordischarged fluid.

Actuator cylinder may be operated by any suitable fluid under pressurebut air under pressure is a convenient and satisfactory fluid. Conduits68 and 72 connect the lower and upper ends of the cylinder 56 with avalve mechanism, indicated generally at 190, which receives air underpressure by means of a conduit 192 connected to a source of air underpressure, not shown. Valve 190 is shown as being manually operated andmay be of any suitable two position type. Pressurized fluid is suppliedto the valve 190 from a suitable source of such pressure by way ofconduit 192. This fluid is directed to the upper end and the lower endrespectively of the cylinder 56 by proper positioning of the valve 190.When fluid pressure is supplied to one end of the cylinder the fluid atthe other end is returned to the valve and vented therefrom by means ofan atmospheric vent port, not shown. This arrangement is well known andneed not be further described.

It is to be understood that while the valve 190 is manually operated itmay be automatically operated by suitable mechanism of any well knowntype.

ln the operation of the apparatus or mechanism, it is to he understoodthat the cylinder moves upwardly and downwardly and is carried orsupported by the shaft 60 which also moves upwardly and downwardly undercertain conditions which are described hereinbelow. Movement of thecylinder is limited at the bottom by engagement of the cylinder bracket78 with the adjustment nut part 94 and is limited in its upward movementby engagement of the bushing or seal 62 with the under side of the block18, it being noted that the diameter of the seal or bushing 62 isgreater than the diameter of the bore 46 so that said bushing or sealwill not enter said bore but will engage the area of the bottom of saidblock 18 immediately about the lower end of said bore 46. With thesyringe installed as illustrated in FIG. 5a, the cylinder bracket 78,cylinder 56, and syringe plunger 174, are adjusted to the zero point onthe syringe scale 172. With the cylinder bushing 62, pressing theunderside of block 18, and the plunger at zero, the cylinder bracket 78,is secured by clamping screw 90.

With the syringe installed as shown in FIGS. 1 and 2 and the cylinder 56in its lower position the cylinder bracket 78 is adjusted by means ofthe enlarged part 94 of the adjustment nut to bring the forward end ofthe syringe plunger to the quantity of discharge required and indicatedon the syringe scale.

With this adjustment made, the operation ofthe mechanism or apparatuswill be best understood by referring to FIG. 5. As shown at (b) of FIG.5 the traveling block 156 is in engagement with the lower magnet 40which magnetically holds the block in its lower portion whereat thevalve 110 is in the fill position. Cylinder 56 is in its upper positionand ready to move downwardly when supplied with pressurized operatingfluid by positioning the valve 190 to supply pressurized fluid to thelower end of said cylinder by way of the conduit 68; that is, pressureis applied at I while pressure above the piston 58 is relieved throughthe conduit 72 and the atmospheric vent port ofthe valve 190.

Since the piston 58 in cylinder 56 is held stationary by magnet 40pressurized fluid in the lower end of the cylinder 56 acts against thelower end wall of the cylinder to force said cylinder downwardly to theposition shown in (c) of FIG. 5. Since the valve 110 is at the fillposition, downward movement of the plunger 173 in the syringe barreddraws fluid into said barrel by way of the conduit 186.

Downward movement of the cylinder 56 is halted when the cylinder bracket78 contacts the adjustment nut. Continued supply of pressurized fluid tothe lower end of the cylinder forces the piston 58 upwardly against themagnetic attraction of the magnet 40 causing the traveling block to moveupwardly into engagement with the magnet 38. The upward movement of thetraveling block 56 causes the rack 162 to rotate the gear 136 and thisin turn causes the valve 110 to be actuated to thedischarge position.The parts are now in the position shown at (d) of FIG. 5. Because thepiston 58 and hence the traveling block 156 do not move until thecylinder has reached one or the other end ofits stroke as limited byengagement of the bearing 62 with the block 18 or by engagement-with theadjustment nut part 98 and there is a pressure build up sufficient toovercome the magnetic attraction of one or the other of the magnets 38and 40 the valve 110 is not actuated from one operative position to theother until there has been a complete filling of the syringe or acomplete discharge thereof. Consequently the amount of liquid repeatedlydischarged by the syringe is consistently the same. The apparatus ormechanism is extremely accurate as required in scientific research.

After the traveling block 156 has been moved to the position shown in(d) of FIG. 5, the valve mechanism 190 is operated to cut off thepressure to the lower end of the cylinder, that is P and supplypressurized fluid to the upper end of the cylinder, as at P The cylinder56 then moves upwardly to its upper limit of movement, as shown at (e)of FIG. 5, which is identical to (a) of FIG. 5. As the cylinder movesupwardly, with the valve 110 in the discharge position, fluid isdischarged from the syringe.

With the air pressure still applied to the upper end of the cylinder 56and the piston 58 is forced downwardly to cause the traveling block 156to move from engagement with magnet 38 to engagement with the magnet 40.

The foregoing is a description of the cycling of the apparatus and afterthe discharge movement of the cylinder while the traveling block is heldby magnet 38, the operating of the mechanism or apparatus starts over at(a) of FIG. 5. It should be noted that the valve mechanism 190 may bethe simplest manual valve control or any automatic mechanism defined bythe use requirements for automatic liquid dispensing.

A scale 198 may be provided for convenient resetting of the mechanism,said scale having a longitudinal slot 200 in its lower end for receptionof a screw 202 screwed into a tapped opening provided therefor in frontend of the lug 16. Thus the scale may be adjusted longitudinally. Thescale is positioned adjacent the cylinder bracket so that one edge ofthe latter is operably positioned as an indicator with respect to saidscale.

Relative to the magnet arrangement it will be apparent that in a broadsense the magnets function as a detent. There may be, of course, otherdetent arrangements to releasably restrain movements of the piston rodand hence actuation of the valve between the fill and dischargepositions. By using a detent mechanism the valve 110 is not actuatedfrom one position to the other until the syringe has been completelyfilled or completely discharged.

I claim:

1. A precision fluid dispenser, comprising:

A. an actuator mechanism including:

a. a cylinder part mounted for reciprocal longitudinal movements,

b. a piston operably disposed in said cylinder, said cylinder havingmeans for connection at opposite sides of the piston with a source ofpressure fluid,

0. a piston rod part to which said piston is secured,

' d. a pair of magnetic detent means mounted in spaced relation to eachother, 7

. a traveling member secured to one of said actuator mechanism part,said traveling member being disposed and movable between said detentmeans and engageable therewith respectively, said detent means eachrestraining said traveling member with a limited force when saidtraveling member is engaged therewith;

and means for limiting reciprocating movements of one of said parts inboth directions, the other part moving from one detent to the other whenmovement of said one part is stopped by said means for limitingreciprocal movement at a respective end of movement of said one part.

2. A precision fluid dispenser, comprising:

A. an actuator mechanism including:

a. a cylinder part mounted for reciprocal longitudinal movements.

b. a piston operably disposed in said cylinder, said cylinder havingmeans for connection at opposite sides of the piston with a source ofpressure fluid.

c. a piston rod part to which said piston is secured.

d. a pair of detent means mounted in spaced relation to each other.

e. a traveling member secured to one of said actuator mechanism parts,said traveling member being disposed and movable between said detentmeans and engageable therewith respectively, said detent means eachrestraining said traveling member with a limited force when saidtraveling member is engaged therewith;

f. and means for limiting reciprocating movements of one of said partsin both directions, the other part moving from one detent to the otherwhen movement of said one part is stopped by said means for limitingreciprocal movement at a respective and of movement of said one part;and

B. a syringe operably connected to said other of actuator parts,movement of said one of said parts effecting filling and discharging ofsaid syringe according to the direction of reciprocal movement of saidone part; a valve; fluid connecting means for connecting the valve tosaid syringe, said valve having syringe filling and syringe dischargingpositions, said valve being operably connected to said other part andactuated thereby from one of said positions to the other when therespective detent means releases said other part and the latter movesthe traveling member to the other detent means.

3. The invention defined by claim 2, wherein the cylinder is the onepart and the piston rod comprises the other part; the detent means eachcomprises a magnet, said magnets being spaced apart; and the travelingmember comprises a traveling armature block being of less thickness thanthe space between the magnets and being adapted to be magnetically heldby either of said magnets depending upon the position of the travelingarmature block, operative movements of the piston rod moving saidarmature block from one magnet to the other when cylinder movement isstopped by the means for limiting reciprocating movements of saidcylinder and moving said valve from one position to the other.

4. The invention defined by claim 3, wherein the syringe comprises abarrel, a piston in said barrel, and a plunger to which said piston isattached, and wherein the valve is fixedly mounted, means for connectingthe valve to the forward end of the syringe barrel for holding saidforward end in position; and a cylinder bracket to which the cylinder issecured for effecting movements of said cylinder bracket with respectivemovements of said cylinder. the free end of the syringe plunger beingsecured .to said cylinder bracket for effecting longitudinal movementsof the syringe plunger with respective movements ofthe cylinder bracket.

5. The invention defined by claim 4, wherein the means for connectingtogether the valve and the forward end of the syringe barrel comprises apair of luer'parts attached respectively to the valve and the syringebarrel, said parts being removably connected together.

6. The invention defined by claim 3, wherein the valve has a valveactuator and the connection between the traveling armature block and thevalve includes a gear connected to said valve actuator and a rackconnected to said traveling armature block, said rack having teethengaging the teeth of the gear for effecting rotative movement of thegear with movements of the traveling armature block from one magnet tothe other.

7. The invention defined by claim 4, including means for adjusting thecylinder relative to the cylinder bracket.

8. The invention defined by claim 3, wherein at least one of the meansfor limiting reciprocal movements of the cylinder is adjustable.

9. The invention defined by claim 1, including means for controlling thesupply of pressure fluid to the respective ends of the cylinder andrelieving pressure at the respective ends of the cylinder opposite theend to which pressure fluid is supplied.

10. The invention defined by claim 9, wherein the means for controllingthe supply of pressurized fluid to the cylinder comprises a valve.

1. A precision fluid dispenser, comprising: A. an actuator mechanismincluding: a. a cylinder part mounted for reciprocal longitudinalmovements, b. a piston operably disposed in said cylinder, said cylinderhaving means for connection at opposite sides of the piston with asource of pressure fluid, c. a piston rod part to which said piston issecured, d. a pair of magnetic detent means mounted in spaced relationto each other, e. a traveling member secured to one of said actuatormechanism part, said traveling member being disposed and movable betweensaid detent means and engageable therewith respectively, said detentmeans each restraining said traveling member with a limited force whensaid traveling member is engaged therewith; f. and means for limitingreciprocating movements of one of said parts in both directions, theother part moving from one detent to the other when movement of said onepart is stopped by said means for limiting reciprocal movement at arespective end of movement of said one part.
 2. A precision fluiddispenser, comprising: A. an actuator mechanism including: a. a cylinderpart mOunted for reciprocal longitudinal movements, b. a piston operablydisposed in said cylinder, said cylinder having means for connection atopposite sides of the piston with a source of pressure fluid, c. apiston rod part to which said piston is secured, d. a pair of detentmeans mounted in spaced relation to each other, e. a traveling membersecured to one of said actuator mechanism parts, said traveling memberbeing disposed and movable between said detent means and engageabletherewith respectively, said detent means each restraining saidtraveling member with a limited force when said traveling member isengaged therewith; f. and means for limiting reciprocating movements ofone of said parts in both directions, the other part moving from onedetent to the other when movement of said one part is stopped by saidmeans for limiting reciprocal movement at a respective end of movementof said one part; and B. a syringe operably connected to said other ofactuator parts, movement of said one of said parts effecting filling anddischarging of said syringe according to the direction of reciprocalmovement of said one part; a valve; fluid connecting means forconnecting the valve to said syringe, said valve having syringe fillingand syringe discharging positions, said valve being operably connectedto said other part and actuated thereby from one of said positions tothe other when the respective detent means releases said other part andthe latter moves the traveling member to the other detent means.
 3. Theinvention defined by claim 2, wherein the cylinder is the one part andthe piston rod comprises the other part; the detent means each comprisesa magnet, said magnets being spaced apart; and the traveling membercomprises a traveling armature block of material attracted by magneticforce, the armature block being of less thickness than the space betweenthe magnets and being adapted to be magnetically held by either of saidmagnets depending upon the position of the traveling armature block,operative movements of the piston rod moving said armature block fromone magnet to the other when cylinder movement is stopped by the meansfor limiting reciprocating movements of said cylinder and moving saidvalve from one position to the other.
 4. The invention defined by claim3, wherein the syringe comprises a barrel, a piston in said barrel, anda plunger to which said piston is attached, and wherein the valve isfixedly mounted, means for connecting the valve to the forward end ofthe syringe barrel for holding said forward end in position; and acylinder bracket to which the cylinder is secured for effectingmovements of said cylinder bracket with respective movements of saidcylinder, the free end of the syringe plunger being secured to saidcylinder bracket for effecting longitudinal movements of the syringeplunger with respective movements of the cylinder bracket.
 5. Theinvention defined by claim 4, wherein the means for connecting togetherthe valve and the forward end of the syringe barrel comprises a pair ofluer parts attached respectively to the valve and the syringe barrel,said parts being removably connected together.
 6. The invention definedby claim 3, wherein the valve has a valve actuator and the connectionbetween the traveling armature block and the valve includes a gearconnected to said valve actuator and a rack connected to said travelingarmature block, said rack having teeth engaging the teeth of the gearfor effecting rotative movement of the gear with movements of thetraveling armature block from one magnet to the other.
 7. The inventiondefined by claim 4, including means for adjusting the cylinder relativeto the cylinder bracket.
 8. The invention defined by claim 3, wherein atleast one of the means for limiting reciprocal movements of the cylinderis adjustable.
 9. The invention defined by claim 1, including means forcontrolling the supply of pressure fluid to the respective ends of theCylinder and relieving pressure at the respective ends of the cylinderopposite the end to which pressure fluid is supplied.
 10. The inventiondefined by claim 9, wherein the means for controlling the supply ofpressurized fluid to the cylinder comprises a valve.